Common Household Pipe Types

PVC: Plastic pipe, most is white in color, some is gray, purple, or light brown. Pipe surface is firm and reasonably hard.

Steel: Gray or silver color, a magnet sticks to it. May be galvanized thus some times called "galvanized pipe".

Polyethylene: Black plastic, more flexible than PVC. Surface is softer, will scratch with fingernail.

Copper: Copper or green color metal. A magnet will not stick to it.

PEX: Plastic pipe, very similar to polyethylene, however it is not black, often red, white or blue color.
Look for "PEX" printed on it.

Finding Pipe Size

Grab a piece of string about 6"(152mm) long, then find the location where your water supply pipe enters the house. Strip away any insulation, so you can get at the pipe and wrap the string around it. Measure how many inches of string it takes to go around the pipe once. Based on the string length use the table below to find your pipe size.

Your string length will vary a little, depending on such unavoidable variables as string stretch, dirt on pipe, manufacturing tolerance, what kind of mood you're in, etc.. *Polyethylene pipe size varies depending on the type of polyethylene pipe, thus a range of sizes.

Maximum Flow

Values are based on 7 feet per second of flow. This is the maximum recommended velocity for water in a pipe. Higher flows greatly increase the risk of water hammer, which can potentially damage the pipe.

WARNING: These values are the maximum safe flows that can be pushed through a pipe. The flows given are not an indication of how much water will be available from a given size of pipe. You should not use this table to determine what size a pipe should be, or how much water you can expect to get from it.